Related papers: Testing Comptonization models using BeppoSAX obser…
Fitting equilibrium dynamical models to observational data is an essential step in understanding the structure of the gaseous hot haloes that surround our own and other galaxies. However, the two main categories of models that are used in…
We build a self-consistent model of a warm scattering corona near an accreting black hole in Kerr geometry, in the regime of slow ($\sim 0.01$ Eddington) mass accretion. An iterative Monte Carlo procedure is developed that incorporates…
We have explored the interplay of star formation and AGN activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft…
We have obtained spectral and timing data on GX 3+1 and Ser X-1. Both sources were observed simultaneously with BeppoSAX and RXTE. The RXTE data is used to provide power spectra and colour-colour diagrams in order to constrain the state…
We perform two-dimensional particle-in-cell simulations of magnetic reconnection in electron-ion plasmas subject to strong Compton cooling and calculate the X-ray spectra produced by this process. The simulations are performed for…
We discuss the properties of a small sample of Seyfert 2 galaxies whose X-ray spectrum changed appearance on time scales of years, becoming reflection-dominated from Compton-thin, or viceversa. A reflection--dominated spectrum is usually…
We describe the analysis of the seven broad-band X-ray continuum observations of the archetypal Seyfert 1 galaxy NGC 5548 that were obtained with XMM-Newton or Chandra, simultaneously with high-energy (> 10 keV) observations with NuSTAR and…
A warm corona has been widely proposed to explain the soft X-ray excess (SE) above the 2--10 keV power law extrapolation in AGNs. In actual spectral fittings, the warm coronal seed photon temperature ($T_{\rm s}$) is usually assumed to be…
One of the open problems for AGN is the nature of the primary X-ray emission: it is likely due to Comptonization of soft UV photons, but the optical depth and temperature of the emitting corona were largely unknown before the launch of the…
We present analysis and spectral fits of the RXTE data from the May/June 1999 outburst of Aql X-1. These data include observations in the rising portion of the hard state, in the soft state, and in the falling portion of the hard state. We…
We report results from the analysis of 21 nearby galaxy clusters, 11 with cooling flow (CF) and 10 without cooling flow, observed with BeppoSAX. The temperature profiles of both CF and non-CF systems are characterized by an isothermal core…
An excess of X-ray emission below 1 keV, called soft excess, is detected in a large fraction of Seyfert 1-1.5s. The origin of this feature remains debated, as several models have been suggested to explain it, including warm Comptonization…
While the temperature of the X-ray corona ($\rm{kT_e}$) in active galactic nuclei (AGN) are known for many sources, its variation, if any, is limited to a handful of objects. This is in part due to the requirement of good signal-to-noise…
We analyze the ASCA spectra accumulated within ~100 kpc radii of 12 of the brightest groups of galaxies. Upon fitting isothermal models (1T) jointly to the ASCA SIS and GIS spectra we obtain fits for most groups that are of poor or at best…
We use galaxy-galaxy lensing to study the statistical properties of the dark matter halos of galaxies. Our data is taken from the COMBO-17 survey which has imaged 1 square degree in 17 optical filters giving accurate photometric redshifts…
We present BeppoSAX observations of the Seyfert 1.8 galaxy NGC1365 in the 0.1--100 keV range. The source was 6 times brighter than during an ASCA observation 3 years earlier. The 4--10 keV flux is highly variable during the BeppoSAX…
We have carried out an extensive X-ray spectral study of the bare Seyfert-1 galaxy MCG--02--58--22 to ascertain the nature of the X-ray reprocessing media, using observations from Suzaku (2009) and simultaneous observations from XMM-Newton…
We study 12 Seyfert 1 galaxies with a high level of optical polarization. Optical light emerging from the innermost regions is predominantly scattered in a polar region above the central engine directly in our line of sight. These sources…
We present new BeppoSAX LECS and MECS observations, covering the energy range 0.1 - 10 keV (observer's frame), of four BL Lacertae objects selected from the 1 Jy sample. All sources display a flat (alpha_x ~ 0.7) X-ray spectrum, which we…
Data derived from general relativistic magnetohydrodynamic simulations of accretion onto black holes can be used as input to a postprocessing scheme that predicts the radiated spectrum. Combining a relativistic Compton scattering radiation…